| The mutton sheep breeds are mostly fat hips,and their hip fat content is very high,and some varieties are even as high as 17%.At present,there are few reports on the research of different varieties of fat-rumped sheep,which limits the application of hip fat in the food industry.In order to make better use of hip fat,used the hip fat of Altay sheep,Kazakh sheep and Bayinbulak sheep as raw materials.Firstly,determined the best extraction method for three varieties of sheep oil,comparative analysis of physicochemical properties and fatty acid composition differences of sheep oil among different breeds.And researched effect of different temperature on iodine value,melting point and fatty acids of sheep oil by solvent extraction.Finally,researched the oxidative stability of sheep oil and its fractionated products.The main results are as follows:(1)To compare the effects of different extraction methods on the extraction rate and physicochemical properties of three varieties of fat-rumped sheep oil,The sheep hip fat were roughly extracted by water bath heating extraction,atmospheric pressure drying and heating extraction,ultrasonic assisted extraction and vacuum heating extraction.The results show:The quality of vacuum heating extracting sheep oil is better than the other three methods.The extraction rate of vacuum heating in Altay sheep was 70.47%.the saponification value was 195.25 mg/g,the iodine value was 47.75 g/100 g,the acid value was 0.80 mg/g,and the melting,point was 39.20℃.The extraction rate of vacuum heating in Kazakh sheep was 71.29%.the saponification value was 196.87 mg/g,the iodine value was 48.36 g/100 g,the acid value was 0.78 mg/g,and the melting point was 38.96℃.The extraction rate of vacuum heating extraction in Bayinbulak sheep was 76.8 1%,the saponification value was 193.94 mg/g,the iodine value was 50.29 g/100 g,the acid value was 0.75 mg/g,and the melting point was 34.20℃.(2)To compare the physicochemical properties and fatty acid differences of three varieties of fat-rumped sheep crude sheep oil,the physicochemical properties and fatty acids of three varieties of fat-rumped sheep oil were analyzed by gas chromatography-mass spectrometry(GC-MS).The results show:Physical and chemical properties and fatty acid composition are also different from different varieties.Altay sheep had the highest saponification value(196.87 mg/g)and Bayinbulak sheep had the highest iodine value(50.29 g/100 g),and the difference between acid value and melting point was not obvious;There were large differences in pentadecanoic acid,heptadecanoic acid,stearic acid,SFA and UFA among the three varieties.The SFA was 48.23%,50.70%,and 41.85%in sequence;the UFA was 5 1.76%,49.13%,and 58.15%in sequence.(3)In order to investigate the effects of different crystallization temperatures on the iodine value,melting point and fatty acids of fractionated products of the three varieties of fat-rumped sheep oil,extraction of sheep oil by stepwise cooling by solvent method,fatty acids were determined in combination with GC-MS.The results show:In the fractionation products,Altay sheep and Kazakh sheep have the highest yield(22.5%,23.10%)in 22℃ solid lipid,the highest yield(30.70%)of liquid lipid was obtained in Bayinbulak sheep at 2 C.The fractionation products of different varieties of fat-rumped sheep oil decreased with the extraction temperature.The melting point decreased significantly(P<0.05),and the iodine value increased significantly(P<0.05).The changes in fatty acid content of Altay sheep,Kazakh sheep,and Bayinbulak sheep oil were the same.The content of the fractionated products SFA decreases as the fractionation temperature decreases,the change in UFA is the opposite of SFA;The components with the highest SFA content were 32℃ solid lipid(54.21%,51.58%,50.34%),the highest UFA content is 2℃ liquid fat(54.39%.55.97%,62.71%);The most obvious fatty acids in SFA are palmitic acid and stearic acid;while the more obvious fatty acid in UFA is 9-octadecenoic acid.(4)To research the effects of different storage conditions on the oxidative stability of sheep oil by solvent method,the single factor test was used to evaluate the acid value and peroxide value,study the effects of temperature,air and light on the oxidative stability of sheep oil.The results show:As the storage time increases,under the 4 ℃,room temperature,aerobic,anaerobic,bright,dull conditions.the acid value and peroxide value of the three varieties of fat-rumped sheep oil and their fractionated products were increased.The change range of liquid lipids in the fractionated products was higher than that of solid lipids,Therefore,sheep oil should be sealed and stored in low temperature,dry and dark environment during processing and storage to extend the storage period. |
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